In the processing and packaging of semiconductor devices, wire and ribbon bonding continues to be a widely used method of electrical interconnection between two locations within a package (e.g., between a die pad of a semiconductor die and a lead of a leadframe). In connection with the formation of wire and/or ribbon loops in certain applications, a cutting portion may be used to cut into the conductive material (e.g. wire or ribbon) to assist in severing the completed wire or ribbon loop from the wire or ribbon supply. U.S. Pat. No. 4,976,392, which relates to wire bonding systems, discloses use of such a cutting portion and is incorporated by reference herein in its entirety.
FIG. 1 illustrates exemplary semiconductor package 10 including semiconductor die 14 which is supported by substrate 16 (e.g. a copper leadframe 16 or other die support structure). Wire or ribbon loop 12 (i.e., conductive material 12) provides electrical interconnection between die 14 and lead 16a of substrate 16. In the example device shown in FIG. 1, wire loop 12 is bonded twice to die 14 (at bonded portions 12b and 12c) and once to lead 16a (at bonded portion 12a).
While most conventional wire bonding sequences form a first bond on a die, and a final bond on a substrate/leadframe, reverse bonding operations are also known. During an exemplary reverse wire (or ribbon) bonding operation, a first bond is formed on lead 16a, thereby forming bonded portion 12a. Then a length of wire is extended towards die 14 where a second bond is formed (bonded portion 12b) on a portion of die 14 (e.g., on a die pad). The wire is further extended to another location on die 14 (bonded portion 12c). After formation of bonded portion 12c, it is desirable to cut the wire to separate the now formed wire loop 12 from the wire supply. A cutting blade is desirably used to at least partially cut through the wire after formation of bonded portion 12c. However, during the cutting of the wire it is possible that the cutting blade may pierce and/or damage a portion of underlying die 14.
More specifically, in FIG. 2A, conventional cutting blade 26 within a wire bonding system is shown in a position prior to contact with wire or ribbon loop 12. FIG. 2B illustrates cutting blade 26 having pierced loop 12 and continuing to contact/pierce at least a portion of underlying semiconductor die 14 at, for example, bonding location 18. Such contact/piercing of die 14 may cause a defect leading to poor performance or operational problems.
Thus, it would be desirable to provide improved cutting blades and associated wire bonding systems.